Electrolytic rectifier



Nov. 29, 1932. R. D. MERsHON ELECTROLYTIC RECTIFIER Filed Dec. 4, 1931 ATTORNEYS INVENTOR 7f 17. Wars/1022:

BY aw u Kw WW Patented Nov. 29, 1932 RALPH I MERSHUTN', OF NEW YORK, N1, .5.

ELECTBULYTIC RECTIFIER Application filed Dccemter 4, 1931., Serial No. 578,993,

This invention relates to electrolytic rectifiers, for converting alternating voltage and current into direct. As is well known, such devices depend for their operation upon the film which may he formed upon the surface of certain. metals and which possesses the peculiar property oi ofierin low resistance to the flow of current from the electrolyte to the metal but relatively high resistance to current tending to flow from the metal to the electrolyte ll, then, an electrode having such a film and an electrode or" non-filming metal or other conducting material are inersed in a suitable electrolyte and the two are connected to a source of alternating current the current impulses which are positive with respect to the filmed electrode will foe suppressed and those which are positiye with m respect to the non-filming electrode will pass through the device, Hence the current from the iilnied electrode will he unidirectional, though. iore or less pulsating in character,

two l ned electrodes are used both current imp es oi each cycle may he rectified, and esultant current will all he in same direction,

By reason of their simplicity and relative ly low cost such devices offer attractive possihilities, hut these possibilities have been found dificult to realize in practice. In the first place, when the filmed electrodes are made pure metal (or metal containing nothing else hut the impurities found in commercial grades, which impurities are usually silicon, titanium and iron, sometimes copper also), the efficiency of the rectifier is low, especially when the electrolyte is hot, as it 1s apt to he by reason of the losses due to the re sistance encountered by the current. Also, the filmed metal is subject to rapid corrosion due to the repeated break-down and re-iormation of the :lilm incident to the rectifying action, These drawbacks are to a considerniche extent overcome by making, the filmed electrodes of an alloy of aluminum, nesiurn and copper, as described and claimed in my copending application Serial No, 317,- dlll, filed November 6, 1928, but in the course of continued investigation I have found that aluminum alloyed with cadmium,

and preferably containing nickel also, is still hotter, as evidenced by longer life and "by high efiiciency even at boiling temperature, Advantageous results can he obtained with less, hut l prefer to use at least about 5 per cent of cadmium and 2 per cent of nickel. A like amount of copper may he used, but 1 corn sider niclrel better. @i the latter element I may use as much as '6 per cent, and in some cases more, but i have not observed that the results are any better than with about 4 per cent, As for the cadmium content l have not found that more than 9.4 per cent offers any material advantage, hut the invention is not limited to that amount since the alloy I may contain cadmium up to the maximum that can he alloyed with aluminum or with aluminum and nickel. Eight or nine, preferahly about eight and a halt, per cent of cadmium is a good average amount, losing satisfactory for impressed voltages exceeding 209 volts (R. M S.) as well as for lower. Using an alloy composed of aluminum 8711" per cent, cadmium 3.7 per cent, and nickel P I 3.6 per cent, approximately, with a con-- denser in parallel with the l). *G, terminals of the rectifier, have obtained an eificieucy as high as 92 per cent or higher, (fine ad vantage of the alloy referred to is that the rectified output has a higher voltage than can 39 he obtained with any other metal that l lrnow of. Instead of nickel I may use other metals such as copper, cobalt, or silicon, but the electrical results are less advantageous. in general 1 may use any one or more of the metals nickel, copper, cobalt and silicon.

My experience indicates that an acid electrolyte, say one containing horax or sodium phosphate and horic or phosphoric acid gives substantially better results in the long run than a neutral or alkaline electrolyte, say one containing only oorax or sodium phosphate or sodium hydroxid. l prefer, however, a solution containing one-half pound of anhydrous sodium tetrahorate and one and a hall pounds of horic acid per gallon of water.

For the non-lilming electrode carbon may he used, or any non-filming metal, preferably one which is not readily deposited on the filming electrodes, as for example high-silicon iron, but I prefer graphite, as it resists well the chemical or electrochemical attack incident to the operation of the rectifier. The metal tank or vessel containing the electrolyte may be used as the non-filming electrode, as is common in the art.

In the accompanying drawing,

Figs. 1, 2, 3, 4 and 5 illustrate diagrammatically various forms of electrolytic rectifiers in which my invention may be embodied.

Throughout the drawing, 10 is a tank or vessel for the electrolyte, 11, 11 are filmed electrodes of aluminum-cadmium-nickel al- 10y, 12 is a non-filming electrode of graphite, T is an auto-transformer or balance coil, R, R are the terminals for the rectified output, one connected to the neutral point of the balance coil and the other to the anode or anodes 12. A, A are the input terminals for connection with a source of alternating volta and current.

In ig. 1 the rectifier has one filming electrode and is therefore of the half-wave type, that is, positive impulses impressed upon the filmed electrode 11 are suppressed and only those which are impressed on the non-filming electrode 12 are passed. In Figs. 2 and 3 two cells such as are shown in Fig. 1 are used for full-wave rectification, in the one case with the filmed electrodes connected to the transformer or balance coil and in the other with the non-filming electrodes connected thereto. In Fig. 4 both filmed electrodes are in the same vessel and only one non-filming electrode is needed. When both filmed electrodes are in the same tank a balance coil or transformer is necessary, as in Fig. 4, for example, and also in the arrangements shown in Figs. 2 and 3, in which only two half-wave cells are used. With four or more such cells they may be connected as in Fig. 5, in which case no balance coil or transformer is needed, though a transformer may be employed as a convenient means for stepping the impressed alternating voltage up or down.

The rectifying operation will be readily understood by tracing the course of the current in an of the figures. For example, assume in ig. 4 an impulse coming in from terminal A. Unable to pass through the film on electrode 11' the current flows through conductor 13 to terminal R, thence through the translating device (not shown) connected to terminals R, R, and from the latter terminal to the non-filming electrode 12, the electrolyte, filmed electrode 11, and thence to the transformer T and out through terminal A. When the alternating voltage reverses the fiow is from terminal A through conductor 13, terminals R, R, unfilmed electrode 12 and filmed electrode 11 to terminal A. In Fig. 5 an impulse coming in at terminfil A flows through unfilmed electrode 12 in the lower tank at the right, filmed electrode 11' in the same tank, conductor 14, terminals R, R, conductor 15, unfilmed electrode 12 in the upper tank at the left, filmed electrode 11 in the same tank, and thence to terminal A. When the alternating voltage reverses, the current flows first through the lower cell at the left and out through the upper cell at the right.

It is to be understood that the invention is not limited to the specific details herein described but can be carried out in other ways without departure from its spirit.

I claim- 1. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy.

2. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy containing nickel.

3. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy containing copper.

4;. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy having a cadmium content not less than about 5 per cent.

5. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy having a cadmium content from 5 per cent to 10 per cent, approximately.

6. An electrolytic rectifier having an electrode made of an aluminum-cadmium alloy containing not less than about 2 per cent of nickel.

7. An electrolytic rectifier havin an electrode made of an aluminum-cadmlum alloy containing from about 2 per cent to 6 per cent of nickel.

8. An electrolytic rectifier having an electrode made of aluminum-cadmium alloy having a cadmium content of from 5 to 10 per cent, approximately, and containing from about 2 to 6 per cent of nickel.

9. An electrolytic rectifier having an electrode made of aluminum-cadmium alloy having a cadmium content of about 8.7 per cent and containing about 3.6 per cent of nickel.

10. An electrolytic rectifier having an electrode made of aluminum-cadmium alloy containing at least one other metal of the class consisting of nickel, cobalt, copper and silicon.

11. An electrolytic rectifier comprising a filmed electrode composed of aluminum-cadmium alloy, at non-filming electrode, and an electrolyte in which said electrodes are immersed, containing a free acid of the class composed of boric and phosphoric acids.

12. An electrolytic rectifier comprising a filmed electrode composed of aluminum-cadmium alloy, a nonfilming electrode, and an electrolyte in which said electrodes are immersed, containing borax and boric acid in solution.

13. An electrode for an electrolytic recti fier, composed of, aluminum-cadmium alloy.

14. An electrode for an electrolytic rectifier, composed of aluminum-cadmium alloy containing nickel.

15. An electrode for an electrolytic rectifier, made of an alloy composed of aluminum about 87.7 'per cent, cadmium about 8.7 per cent, and nickel 3.6 per cent, approximately,

In testimony whereof I hereto aflix my sig nature.

RALPH D. MERSHON. 

